Nicolas Alvarez <nic### [at] gmailcom> wrote:
> After months of running Ubuntu, I discovered it was throttling the CPU. I
> keep nice 19 processes using 100% CPU 24/7, and I want all the speed I can
> get from the CPU.

> (they're nice 19 just so they don't make the desktop slower, I still want
> them to run as fast as they can)

  In my experience even if there is only one single CPU-intensive process
running at nice level 19 it will run slower than if it was running eg. at
nice level 4 (which is the default for nice when you don't specify a number).

  I'm not exactly sure why this is so nor do I have any references to this,
but it's what I have experienced. Maybe a process at nice level 19 really
is at the very bottom of the barrel and *anything* will override it, no
matter how light. For this reason whenever I want to make a process (such
as povray) run with a lower scheduling priority I just use the default nice
level (ie. 4). That seems to give basically all free CPU to the process but
will not hinder other processes which temporarily need it more. Also in this
case the nice 4 process still gets a fair share of the CPU and doesn't get
completely halted.

  Also in my experience nice level 4 is completely enough to keep a heavy
process, well, nice. For example I have run long povray renders with nice
level 4 and at the same time watched videos with mplayer without any
problems.

  I suppose the only cases where you want to use a nice value different
from 4 is when you want two or more heavy processes running at the same
time and you want one of them getting more CPU than the others. The
difference in priorites will affect how the CPU is shared between them.

-- 
                                                          - Warp

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